In a camera platform system of a ceiling hanging type such as a surveillance camera, when shooting an object approaching from a front side with tracing it using a tilt-rotating camera, the object in an image obtained after passing a position immediately under the camera is turned upside down if any image processing is performed. Therefore, when the tilt angle of the camera becomes a predetermined set angle (for example, 90 degrees by which the camera faces a directly-downward direction), a function that performs a reverse processing by 180 degrees of the shot image to correctly display top and bottom of the object is provided in many cases.
Japanese Patent Laid-Open No. 2003-289466 discloses a method of generating a display image for which a reversing processing is performed so as to have a normal top-and-bottom relationship by changing a reading method of the shot image from the memory which is provided to tentatively store the shot image when a tilt angle of the camera with respect to the ceiling is equal to or larger than 90 degrees.
However, in the method disclosed in Japanese Patent Laid-Open No. 2003-289466, in spite of the fact that a tilt rotation direction of the camera does not change, since a traveling direction of the object in the display image suddenly changes by the reverse processing, a user who observes the object gets nervous and has a sense of incompatibility in the operation.
Moreover, when the object goes or comes at a position immediately under the camera, the traveling direction of the object cannot be determined, and the confusion may occur in the operation to trace the object.